Android学习之Camera

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一、调用系统camera

	btn_camera.setOnClickListener{
	val intent = Intent(MediaStore.ACTION_IMAGE_CAPTURE)

	//直接调用，不获取返回值
	startActivity(intent)

	//获取返回结果，可对结果进行操作。
	startActivityForResult(intent, requestCode:1)
}

二、获取返回结果，显示压缩图

此方法显示的图片为压缩图

override fun onActivityResult(requestCode:Int, resultCode:Int, data:Intent?){
	super.onActivityResult(requestCode, resultCode, data)
	if(resultCode == RESULT_OK)
	{
		if(requestCode == 1)
		{
			val bitmap = data?.extras?.get("data") as Bitmap
			image.setImageBitmap(bitmap) 
		}
	}
}

三、完整显示图片

1. 修改setOnClickListener

	val intent = Intent(MediaStore.ACTION_IMAGE_CAPTURE)
	val photoUri = FileProvider.getUriForFile(this, "Camera.fileProvider", File("$path/test123.png"))
	intent.putExtra(MediaStore.EXTRA_OUTPUT, photoUri)
	startActivityForResult(intent, 2)

2. 修改onActivityResult

override fun onActivityResult(requestCode:Int, resultCode:Int, data:Intent)
{
	super.onActivityResult(requestCode, resultCode, data)
	if(resultCode == RESULT_OK)
	{
		if(requestCode == 1)
		{
			......
		}
		else if(requestCode == 2)
		{
			//1. 通过读取文件，转换成bitmap显示
			val fis = FileInputStream(path)
			val bitMap = BitmapFactory.decodeStream(fis)
			image.setImageBitmap(bitMap)
			fis.close()
			//上面方法注意打开关闭文件时可能出现异常， 需要增加try  catch  捕捉异常。
			
			//2.通过uri显示
			val pUri = Uri.fromFile(File(path))
			image.setImageURI(pUri)
		}
	}
}

此方法需注意图片文件是否创建成功，创建不成功时可能出现异常。
对于高版本的Android系统。无法通过原始的Uri.formFile函数获取Uri。所以需要通过FileProvider来获取。具体操作方法可以参考通过File Provider获取Uri

四、自定义相机

1. 创建自定义相机类

class MyCameraActivity:Activity(){
	private lateinit var mCamera:Camera
	private lateinit var mHolder:SurfaceHolder
	override fun onCreate(savedInstanceState:Bundle?){
		super.onCreate(savedInstanceState)
	//需要获取照相机使用权限。 代码省略
	
	setContentView(R.layout.my_camera)
	mHolder = my_camera_view.getHolder()
	mHolder = addCallback(this)
	}
}

1.1 获取系统相机。

	private fun getCamera():Camera{
		return Camera.open()
		
	}

1.2 实时显示相机内容。

fun startAction(camera:Camera, holder:SurfaceHolder){
	camera.setPreviewDisplay(holder)
	camera.setDisplayOrientation(90)
	camera.startPreview()
}

1.3 释放相机资源

	fun releaseCamera(){
		if(mCamera != null){
			mCamera.setPreviewCallback(null)
			mCamera.stopPreview()
			mCamera.release()
			mCamera = null
		}
}

1.4 camera 生命周期绑定

	override fun onResume(){
		super.onResume()
		if(mCamera == null)
			mCamera = getCamera()
			if(mHolder != null)
			{
				startAction(mCamera, mHolder)
			}
	}

	override fun onPause(){
		super.onPause()
		releaseCamera()
	}

1.5 实现SurfaceHolder.Callback接口

override fun surfaceCreated(holder:SurfaceHolder){
	startAction(mCamera, mHolder)
}

override fun surfaceChanged(holder:SurfaceHolder, format:Int, width:Int, height:Int){
	mCamera.stopPreview()
	startAction(mCamera, mHolder)
}

override fun surfaceDestroyed(holder:SurfaceHolder){
	releaseCamera()
}

1.6 实现相机预览时点击预览界面相机自动对焦功能

my_camera_view.setOnClickListener{mCamera!!.autoFocus(null)}

2. 添加Camera使用权限

AndroidManifest.xml

	<uses-permission android:name="android.permission.CAMERA"/>

<!-- 添加activity -->

<activity android:name=".MyCameraClass"/>

3. 主页面添加按钮打开myCamera页面

MainActivity.kt

	mycamerabtn.setOnClickListener{
	startActivity(Intent(this, MyCameraClass::class.java))
}

4. 添加拍照响应函数

	btn_my_camera.setOnClickListener{
		var parameters = mCamera!!.parameters
		parameters.pictureFormat = ImageFormat.JPEG
		parameters.setPictureSize(800, 400)
		parameters.focusMode = Camera.Parameters.FOCUS_MODE_AUTO
		mCamera!!.autoFocus(object:Camera.AutoFocusCallback{
			override fun onAutoFocus(success:Boolean, camera:Camera?){
			mCamera!!.takePicture(null, null, object:Camera.PictureCallback{
				override fun onPictureTaken(data:ByteArray?, camera:Camera?){
				if(success){
					File("/sdcard/Pictures/temp.png").writeBytes(data!!)
					this@MyCameraActivity.finish()
					}
				
				})
			}
		}
	})
}

5. 添加拍照后显示界面

5.1 创建拍照显示页面布局

	<ImageView
		android:id="@+id/pic_show"
		android:layout_width="mactch_parent"
		android:layout_height="0dp"
		android:layout_weight="1"/>
	<Button
		android:layout_width="wrap_content"
		android:layout_height="50dp"
		android:text="back"
		android:id="@+id/btn_back"/>

5.2 创建拍照显示页面类

class resultActivity:Activity(){
	override fun onCreate(savedInstanceState:Bundle?){
		super.onCreate(savedInstanceState)
		setContentView(R.layout.picture_show)
		
		val picPath = intent.getStringExtra("picPath")
		val fis = FileInputStream(picPath)
		var bitmap = BitmapFactory.decodeStream(fis)
		val matrix = Matrix()
		matrix.setRotate(90F)
		bitmap = Bitmap.CrateBitmap(bitmap,0,0,bitmap.width,bitmap.height, matrix, true)
		pic_show.setImageBitmap(bitmap)
	}
}

6. 相机水印功能

修改相机显示布局
原始代码：

    <SurfaceView
        android:id="@+id/my_camera_view"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"/>

修改后：

 <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1">

        <SurfaceView
            android:id="@+id/my_camera_view"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentStart="true"
            android:layout_alignParentLeft="true"
            android:layout_alignParentEnd="true"
            android:layout_alignParentRight="true"
            android:layout_alignParentBottom="true"
            android:layout_marginStart="56dp"
            android:layout_marginLeft="56dp"
            android:layout_marginEnd="55dp"
            android:layout_marginRight="55dp"
            android:layout_marginBottom="92dp"
            android:text="Nova 7 / 2021 - xx - xx HH:MM:SS"
            android:textColor="#ea3826"
            android:textSize="20sp" />

    </RelativeLayout>

说明：此处仅修改了显示预览时的水印，实际拍照后保存的照片中不含有水印。

7. 显示界面添加按钮返回功能

        btn_back.setOnClickListener(){
            startActivity(Intent(this, MyCameraClass::class.java))
        }